In recent years, portable radio apparatuses have become widely used. In the portable radio apparatus, since importance has been attached to portability and since communication quality has also been required to be improved, the design of antenna elements has become important.
A foldable portable telephone described in Patent Document 1 as will be described below proposes a technique in which, by supplying electric power to a shield case provided in at least one of the housings of the portable telephone, the housing is made to operate as an antenna so as to reduce gain change depending on the state of a user's hand holding the portable telephone. Further, a configuration in which a rod antenna is jointly used is also proposed. For example, in the foldable (clamshell) portable telephone disclosed in Patent Document 1 as will be described below, a rod antenna is provided in a lower case (housing), and the proximal end section (feeding section) of the rod antenna is connected to an output terminal of a transmission circuit. In this technique, the shield box provided in the lower case (housing) is used as an antenna and the rod antenna is also used. This makes it possible to obtain a high gain and to reduce the gain change depending on the state of the hand of the user of the portable telephone.    Patent Document 1: JP Patent No. 3830773 (see in particular FIG. 5 and FIG. 13, and the related description in the specification)